§ 73.44 AM transmission system emission limitations.
(a) The emissions of stations in the AM service shall be attenuated in
accordance with the requirements specified in paragraph (b) of this
section. Emissions shall be measured using a properly operated and
suitable swept-frequency RF spectrum analyzer using a peak hold
duration of 10 minutes, no video filtering, and a 300 Hz resolution
bandwidth, except that a wider resolution bandwidth may be employed
above 11.5 kHz to detect transient emissions. Alternatively, other
specialized receivers or monitors with appropriate characteristics may
be used to determine compliance with the provisions of this section,
provided that any disputes over measurement accuracy are resolved in
favor of measurements obtained by using a calibrated spectrum analyzer
adjusted as set forth above.
(b) Emissions 10.2 kHz to 20 kHz removed from the carrier must be
attenuated at least 25 dB below the unmodulated carrier level,
emissions 20 kHz to 30 kHz removed from the carrier must be attenuated
at least 35 dB below the unmodulated carrier level, emissions 30 kHz to
60 kHz removed from the carrier must be attenuated at least [5 + 1
dB/kHz] below the unmodulated carrier level, and emissions between 60
kHz and 75 kHz of the carrier frequency must be attenuated at least 65
dB below the unmodulated carrier level. Emissions removed by more than
75 kHz must be attenuated at least 43 + 10 Log (Power in watts) or 80
dB below the unmodulated carrier level, whichever is the lesser
attenuation, except for transmitters having power less than 158 watts,
where the attenuation must be at least 65 dB below carrier level.
(c) Should harmful interference be caused to the reception of other
broadcast or non-broadcast stations by out of band emissions, the
licensee may be directed to achieve a greater degree of attentuation
than specified in paragraphs (a) and (b) of this section.
(d) Measurements to determine compliance with this section for
transmitter type acceptance are to be made using signals sampled at the
output terminals of the transmitter when operating into an artificial
antenna of substantially zero reactance. Measurements made of the
emissions of an operating station are to be made at ground level
approximately 1 kilometer from the center of the antenna system. When a
directional antenna is used, the carrier frequency reference field
strength to be used in order of preference shall be:
(1) The measure non-directional field strength.
(2) The RMS field strength determined from the measured directional
radiation pattern.
(3) The calculated expected field strength that would be radiated by a
non-directional antenna at the station authorized power.
(e) Licensees of stations complying with the ANSI/EIA-549-1988, NRSC-1
AM Preemphasis/Deemphasis and Broadcast Transmission Bandwidth
Specifications (NRSC-1), prior to June 30, 1990 or from the original
commencement of operation will, until June 30, 1994, be considered to
comply with paragraphs (a) and (b) of this section, absent any reason
for the Commission to believe otherwise. Such stations are waived from
having to make the periodic measurements required in § 73.1590(a)(6)
until June 30, 1994. However, licensees must make measurements to
determine compliance with paragraphs (a) and (b) of this section upon
receipt of an Official Notice of Violation or a Notice of Apparent
Liability alleging noncompliance with those provisions, or upon
specific request by the Commission.
[ 47 FR 8588 , Mar. 1, 1982, as amended at 49 FR 3999 , Feb. 1, 1984]
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